The modified Dunn procedure can be performed safely in stable slipped capital femoral epiphysis but does not alter avascular necrosis rates in unstable cases: A large single-centre cohort study

Abstract

Purpose: The modified Dunn procedure for slipped capital femoral epiphysis (SCFE) remains controversial. We reviewed our series over ten years to report our learning curve, experience with intraoperative monitoring of femoral head perfusion and its correlation with postoperative Single-photon emission computed tomography (SPECT-CT) bone scan and femoral head collapse in stable and unstable SCFE. Methods: We retrospectively assessed 217 consecutive modified Dunn procedures performed between 2008 and 2018. In all, 178 had a minimum of one-year follow-up (mean 2.7 years (1 to 9.2)) including 107 stable and 71 unstable SCFE. Postoperative viability was assessed with a three-phase Tc99 bone scan and SPECT-CT. From 2011, femoral head perfusion monitoring was performed intraoperatively using a Codman Intracranial Pressure transducer and the capsulotomy was modified. Results: With intraoperative monitoring, the rate of non-viable femoral heads in stable SCFE decreased from 21.1% to 0% (p < 0.001). In unstable SCFE, the rate remained unchanged from 35.7% to 29.8% (p = 0.669). The positive predictive value (PPV) of pulsatile monitoring for no collapse was 100% in stable and 89.1% in unstable SCFE. Pulsatile monitoring and viable SPECT-CT bone scan gave a 100% PPV for all cases. A non-viable scan defines those hips at risk of collapse since 100% of stable and 68.2% of unstable hips with non-viable bone scans went on to collapse. Conclusion: Our protocol enables safe performance of this complex procedure in stable SCFE with intraoperative monitoring being a reliable asset. The avascular necrosis rate for unstable SCFE remained unchanged and further research into its best management is required. Level of evidence: Level III

Intraoperative Epiphyseal Perfusion Monitoring Does Not Reliably Predict Osteonecrosis Following Treatment of Unstable SCFE

“…Our data suggests that epiphyseal perfusion monitoring is not 100% reliable, and it is important to counsel patients and their families that demonstration of epiphyseal perfusion intraoperatively after closed reduction does not preclude the development of osteonecrosis as has been previously reported 7 . Given a 30% rate of AVN following closed reduction with a detectable waveform demonstrated intraoperatively in this series, it may be reasonable to consider follow-up advanced imaging such as a bone scan or perfusion MRI (with metal suppression) in these patients with the goal of early diagnosis and treatment of AVN before femoral head collapse 14 . However, these recommendations are outside of the scope of this study.…”

“…7 Given a 30% rate of AVN following closed reduction with a detectable waveform demonstrated intraoperatively in this series, it may be reasonable to consider follow-up advanced imaging such as a bone scan or perfusion MRI (with metal suppression) in these patients with the goal of early diagnosis and treatment of AVN before femoral head collapse. 14 However, these recommendations are outside of the scope of this study.…”

“…11 While there is no case of AVN reported in the literature following closed reduction with documented intraoperative perfusion, there have been cases of AVN reported after demonstrated perfusion during open reduction. 10,[12][13][14] Regardless, limited data exists regarding the reliability of intraoperative epiphyseal perfusion monitoring to predict the development of AVN. The purpose of this study was to evaluate the reliability of perfusion monitoring and determine whether the presence or absence of a waveform can reliably predict the occurrence of AVN.…”

“…Previous studies have reported variable rates of AVN after treatment for unstable SCFE (0% to 58%) with a meta-analysis suggesting the rate to be ∼24% 11 . While there is no case of AVN reported in the literature following closed reduction with documented intraoperative perfusion, there have been cases of AVN reported after demonstrated perfusion during open reduction 10,12–14 . Regardless, limited data exists regarding the reliability of intraoperative epiphyseal perfusion monitoring to predict the development of AVN.…”

Subcapital realignment osteotomy for the treatment of moderate and severe slipped upper femoral epiphysis: A retrospective study of 123 hips in a tertiary center

“…17,21,[24][25][26][27][28][29][30][31][32] It is important to note that the available literature consists predominately of small retrospective case series with few studies consisting of more than 50 patients. Birke et al 33 recently published their experience in >200 patients and reported that 14.6% of their hips had AVN on the postoperative SPECT-CT bone scan. Their cohort, similar to our own, likely represents the rate of AVN of patients who are treated in high-volume centers.…”